1. Field of the Invention
The present invention relates to a form cylinder in a rotary printing machine and, more particularly, to a form cylinder including a printing foil, covering its outer surface, the respective ends of the printing foil being attached to winding rollers rotatably mounted within the interior of the form cylinder and including a driving device for turning the winding rollers.
2. Description of the Prior Art
Form cylinders of this type are well-known. For example, German Patent Application DE 43 03 872 A1 discloses a form cylinder covered on its outer surface by a printing foil constituting the printing form for the particular printing process being carried out. The beginning and end of the printing foil are stored in the interior of the form cylinder and connected between a first roller and a second roller; the first roller having the unused printing foil wound around it and the second roller having the used or printed printing foil wound around it. The form cylinder includes a driving device for driving either the first or both rollers in order to transport new, unused printing foil from the first roller onto the outer surface of the form cylinder and at the same time to wind the used or printed portion of the printing foil around the second roller after the printing image of the printing foil has been printed on the outer surface of the form cylinder. The portion of the printing foil which then rests on the outer surface of the form cylinder constitutes the basis for a lithographic printing process. Either the printing foil already carries a finished printing image, or it is directly imaged within the printing machine, using either the ink-jet process, thermotransfer, or laser beams, especially laser ablation.
In order to move the printing foil forward the machine includes a driving device, for example, a motor. The driving device is located within the form cylinder.